Is the bytecode changed after compilation?

Question

Java

If so, why does the JVM need metadata? In c#, for example, an assembly stores bytecode, resources, and metadata.

Answer 1

Metadata is stored in .class files, as well as in dll assemblies. They can be obtained using reflection.
For example:
Class className = Person.class;
Annotation[] annotations = className.getAnnotations();
PS - Java uses annotations to bind metadata, while C# uses attributes.